Booster pumps



July 24, 1962 H. E. ADAMS 3, 9

BOOSTER PUMPS Original Filed Nov. 15, 1951 7 Sheets-Sheet 1 IN V EN TOR.

WZMIA, M m

H. E. ADAMS BOOSTER PUMPS July 24, 1962 7 Sheets-Sheet 2 Original Filed Nov. 15, 1951 Y July 24, 1962 3,045,602

H. E. ADAMS BOOSTER PUMPS Original Filed Nov. 15, 1951 7 Sheets-Sheet 3 INVENTOR. fl Ao E. son vs July 24, 1962 H. E. ADAMS 3,045,

v BOOSTER PUMPS Original Filed Nov. 15. 1951 '7 Sheets-Sheet 4 Fig.6

INVENTOR. #flbw a. pop/rs July 24, 1962 Original Filed Nov. 15. 1951 H. E. ADAMS BOOSTER PUMPS 7 Sheets-Sheet 5 INVENTOR. xmkoio e. Ans/vs hire This case is a divisional application of applicants copending application Serial No. 256,580 filed November 15, 1951, now U.S. Patent No. 2,956,504.

This invention relates to booster pumps, particularly fuel booster pumps for aircraft engines. The novel fuel booster pump of the present application is particularly designed to be used in the fuel line between a tank mounted booster pump and the main fuel pump of the engine, but is also adapted for other uses. The novel pump is desirably like the combined centrifugal and vacuum pumps disclosed in United States Patent No. 2,461,865, and in my pending applicaiton Ser. No. 652,- 633 filed March 7, 1946, now U.S. Patent No. 2,581,828, issued January 8, 1952, for Pumps, but embodies further improvements especially adapted to meet the exacting requirements of line mounted booster pumps.

Because of the increased capacity required of the main engine fuel pump of an aircraft engine, it has become necessary to increase the pressure of liquid supplied to the inlet of this pump in order to prevent cavitation and vapor locking within the pump inlet passages. This pressurization has been furnished by a centrifugal booster pump mounted in the fuel tank, by pressurizing the tank, or, in some instances, by an auxiliary line mounted posi tive type fuel booster pump.

With the still greater increase in fuel requirements of the present-day aircraft engine, particularly of the gas turbine type engine, there have developed increased pressure losses in the fuel line between the fuel tank and the main engine pump inlet, together with an increased pressure requirement at the main engine pump inlet because of the greater capacity of the latter pump. Both of these factors have imposed the necessity that constantly higher pressures and flows be supplied by the tank mounted booster pump. This, in turn, has increased the weight of the required tank mounted pump, and has also increased the driving power required therefor.

All these requirements tend to approach or exceed the practical limits of weight and available electric power for booster pumps. The main engine fuel pump must be increased in size, which seems impractical, or, as disclosed herein, it may be supplemented by a line booster pump driven directly by the engine and mounted on the engine itself to pressurize its own main fuel pump.

The engine mounted line booster pump does not do away with the tank mounted booster pump. It merely reduces the discharge requirement from the tank mounted booster pump. The tank mounted booster is necessary for the prevention of vapor locked in the fuel lines, even when the engine driven booster pump is present.

The line mounted booster pump is required to deal with conditions of considerably greater severity than those encountered in the operation of a tank mounted booster pump.

When the fuel in a tank is caused to vaporize or boil because of the reduced ambient absolute pressure as the aircraft climbs, it is diflicult to pump. Under such con-' ditions, either the fuel supply tank must be pressurized to bring the absolute pressure in the tank above the vapor pressure of the fuel, or, if the tank is vented to the atmosphere, resort must be had to a tank mounted fuel booster pump capable of handling this boiling fuel, as

rates Patent ice disclosed for example in Patent No. 2,461,856 and Serial No. 652,633.

Although, in the fuel tank the whole body of fuel is boiling, most of the vapors escape to the free surface at the top of the tank and pass out through the vent. Only a very small proportion of the vapor is drawn through the inlet of the pump from the tank. The tank mounted pump, therefore, is required to handle only a small proportion of the vapors given off by the fuel in the tank.

In the case of a fuel line, however, supplying fuel to the pump, none of the vapor that is released from the time the fuel leaves the tank until it reaches the pump suction can escape. The whole mixture is carried on by the velocity of the fuel in the line to the inlet of the pump, where all of the vapors evolved from the fuel must be handled by the pump, if pumping is to continue.

'In the line there is a friction loss, and consequently a pressure drop, between the point where fuel leaves the tank and where it enters the inlet of the line booster pump. This reduction in pressure, due to frictional resistance, reduces the absolute pressure of the fuel trapped in the line below the fuel vapor pressure, causing vapors to be evolved in the line all of which vapors must be handled by the pump. Thus, the problem of pumping boiling liquids in an enclosed suction line is considerably more diflicult than that of pumping liquids from a tank.

Where relatively small flows have been involved with resultant lower pressure drops, positive type line booster pumps such as vane or gear pumps have been successfully used. These pumps have to be proportioned, however, so that they will handle a total displacement equal to the liquid fuel to be handled, plus the vapors given oil? by the fuel in its travel from the tank to the entrance of the positive type booster pump.

With the increase in flow rate and resulting increased pressure drop, together with the increased volatility of aircraft turbine fuels, the proportion of vapor to liquid has grown to such an extent as to make impracticable the employment of positive type booster pumps. In other words, the size and weight of the required pump would be prohibitive.

It is well known, of course, that a centrifugal pump will handle considerably larger volume for pump weight than will a positive type pump, but it is also well known that a conventional centrifugal pump for liquid is extreme ly sensitive to the presence of gas or vapor, and that its pumping action will break down when the gas or vapor component constitutes more than three percent by volume of the mixed fluid to be handled.

A combined centrifugal and vacuum pump of the type as exemplified in Patent No. 2,461,865 and Serial No. 652,563, has unique provision for the separation, removal and recompression of the vapors. It has been found that this type of pump can be used on pipe line applications by increasing the separating proportions of the liquid pump and increasing the vapor handling proportions of the vacuum pump or compressor, and then returning the recompressed vapors to the fuel tank. This type of pump is now being extensively used as an engine driven booster pump in the manner referred to.

In the simplest engine driven line booster pump of this kind, the vapors are returned by a separate pipe line back to the fuel tank from which they started, or to some other fuel tank. The vapor removing and compressing element in sending the removed vapors back to the tank has to pressurize the gases and vapors sufliciently to overcome pipe friction and any static head difference between the pump and the receiving tank. This pressure difference, though greater than has to be maintained in the case of the tank mounted fuel booster pump, is still relatively low.

It is not always convenient to return the removed gases and vapors to a fuel tank, however, in which case the only place for the vapors to be discharged would be to the line that carries the liquid discharged by the booster pump to the main fuel pump inlet. Because of the higher intermediate pressure between the line booster pump discharge and the main fuel pump inlet, the vapors removed from the suction side of the booster pump would have to be compressed sufficiently to cause them to be substantially completely recondensed. Any uncondensed vapor residue and any uncondensable gases would be so small in volume, however, because of the high pressure, as to have no substantial adverse effect upon the main fuel pump. The compression of these vapors from the booster pump inlet absolute pressure to the booster pump outlet absolute pressure, of course, requires greater power because of the greater pressure difference, as compared with the pressure differential required to deliver these same vapors back to the fuel tank.

It is a primary object of the present invention to provide a liquid booster pump in combination with a compressor capable of drawing off the vapor and gases at the intake side of the pump, and of recompressing them sufiiciently to admit of their recombination with the liquid at the discharge side of the pump.

It is a more specific object to provide a centrifugal liquid pump capable of separating entrained gas and vapor from the liquid, together with a compressor of the hydroturbine type driven in unison with the liquid pump and arranged to draw off the vapor and gas from the intake side of the liquid pump, to compress the gas, compress and recondense the vapor, and then to combine its output with the liquid pump output.

To this end it is a feature, in accordance with one practical and advantageous embodiment of the invention, that the discharge pressure of the compressor is made at least equal to that of the liquid pump by making the rotor diameter of the compressor approximately the same as the impeller diameter of the liquid pump.

It is necessary that the centrifugal liquid pump be designed to give the required full pressure at low engine speeds. When the engine is operating at normal speed, the centrifugal liquid pump, therefore, is generating a much higher pressure than is required. This is because of the well known characteristic of centrifugal pumps that the pressure generated varies as the square of the rotational speed, whereas capacity varies as the first power of the rotational speed. These same characteristics are inherent in the hydroturbine vacuum pump or compressor. During normal operation of the engine, therefore, both the centrifugal liquid pump and the compressor of the combination referred to in the preceding paragraph would be operating to deliver considerably higher pressures than are actually necessary. In the case of some aircraft or gas turbine fuel systems, it is desirable to maintain the natural pressure of the main engine fuel pump at some regullated pressure. Where booster pumps are used which generate wide variations in pressure because of variations in speed, it has been the practice to interpose some form of regulating valve to maintain the desired inlet pressure to the main engine fuel pump.

As the engine speed is decreased toward idling speed, the required vapor and liquid can be also decreased. Because of the characteristics of the fuel system, the frictional drop in the inlet piping diminishes rapidly with the reduced liquid flow, so that the vapors required to be handled by the compressor decrease even out of proportion with the decreased rotational speed. If, therefore, the compressor is made adequate to meet the vapor handling requirements at the normal operating speed of the engine, and adequate to furnish the pressure required at the inlet of the main engine fuel pump at that speed, the necessity for making the compressor capable of delivering the same pressure as the associated liquid pump may be avoided by throttling down the discharge Pressure of the liquid pump to the required inlet pressure of the main fuel pump, and combining the compressor output with the liquid pump output only after the latter has been throttled down.

It is accordingly a further feature, in accordance with another practical and advantageous embodiment of the invention, that the compressor, though constructed to produce a lower discharge pressure than the liquid pump, is enabled to combine its output with that of the liquid pump by providing a liquid perssure reducing valve at the discharge side of the liquid pump.

It is a still further feature that a combined liquid pump and compressor unit is provided, capable of handling the gas and vapor on the one hand and the liquid, on the other, in the compressor and the liquid pump respectively, and of recombining the pump and compressor outputs, but further adapting for convenient alteration to divert the compressed gas and vapor back to the source of liquid supply in any organization in which such diversion is deemed preferable.

Other objects and advantages will hereinafter appear.

In the drawing forming part of this specification FIG. 1 is a longitudinal sectional view of a combined line pump and compressor embodying one form of the invention, the section being taken upon the line 11 of FIG. 4 looking in the direction of the arrows;

FIG. 2 is a fragmentary, longitudinal sectional view of the same structure, the section being taken upon the line 2-2 of FIG. 4 looking in the direction of the arrows;

FIG. 3 is a further longitudinal sectional view of the same structure, the section being taken upon the line 33 of FIG. 4 looking in the direction of the arrows;

FIG. 4 is a transverse sectional view taken upon the line 44 of FIG. 1 looking in the direction of the arrows;

FIG. 4a is a transverse sectional view through the compressor, the section being taken upon the line 4a- 4a of FIG. 1, looking in the direction of the arrows;

FIG. 5 is a view in side elevation of a portion of the pump casing with a cover plate removed;

FIG. 6 is a view of one of two alternative cover plates adapted to be applied to the complementary portion of the casing member shown in FIG. 5 when the compressed gas and vapor are to be returned to a fuel tank;

FIG. 7 is a view of an alternative cover plate which is substituted when the compressed gas and vapor are recombined with the liquid en route to the main fuel P p;

FIG. 8 is a fragmentary sectional view similar to FIG. 2 but illustrating a modified pump and compressor combination in which the compressor is capable of delivermg as high a discharge pressure as the centrifugal liquid P p;

FIG. 9 is a longitudinal sectional view of a duplex liquid pump and compressor combination in which a single compressor serves both working chambers of the liquid pump, the section being taken upon the line 99 of FIG. 10 looking in the direction of the arrows;

FIG. 10 is an end view, partly broken away, of the pump and compressor combination of FIG. 9, the planes of the portions shown in section being substantially indicated by the line 1010 of FIG. 9, looking in the direction of the arrows;

FIG. 11 is a fragmentary sectional view taken upon the line 11-11 of FIG. 10, looking in the direction of the arrows; and

FIG. 12 is a fragmentary sectional view taken upon the line 12--12 of FIG. 10, looking in the direction of 7 the arrows.

casing member 3 is provided with threaded bores 7 which are adapted to receive the threaded bodies of headed screws (not shown) for ciamping the casing upon a flanged fuel supply pipe section (not shown) in axial alignment therewith.

The unit -1 includes liquid impeller blades 8 and compressor rotor blades 9, both of which are desirably made integral with a driving disc 10. A flange 12 of the disc is revolubly received within an annular flange 13 which forms part of a stationary compressor body member 14.

An annular groove 11 is formed in the body member 14 and forms part of a seal chamber between the liquid end and the vapor end of the impeller-rotor. This chamber is connected to the interior of the liquid impeller passageways by a bore 11x, to avoid the building up of excessive pressure between the impeller shroud and the lobe seal and thereby to avoid flooding of the vapor pump.

The disc 10 is secured upon a driving shaft 15 to be driven in unison with the shaft by means of a key 16. The hub of the disc 10 is secured upon a reduced portion 17 of the shaft 15. The left hand hub face of the disc 10 (as viewed in FIGURE 1) bears against a washer 18, which washer in turn bears against a shoulder 19 of the shaft 15. A second washer 20 bears against the right hand hub face of the disc 10, being pressed against the disc by a nut 21 which is threaded onto a further reduced end portion 22 of the shaft 15.

The driving, bearing and sealing details of the shaft 15 form no part of the present invention. Briefly, the intermediate portion of the shaft is supported in a stationary bearing 23. A sylphon bellows 24 sealed to the shaft 15 through its head 25 at one end, carries at its opposite end a bearing ring 26 which is pressed by the bellows into bearing engagement with an end face of the bearing 23.

An enlarged portion 27 of the shaft 15 carries the inner race 28 of a ball bearing 29, the outer race 30 of which is secured in a cup portion 31 of the casing member 2. The shaft 15 is adapted to be connected to an enginedriven shaft (not shown) through a splined coupling, the shaft being formed with a splined end 35 for mating with a complementary recess of the engine driving shaft.

The compressor body member 14 is formed interiorly to provide two opposed eccentric lobes 33 and 34. As is well understood, the rotor blades 9 divide the rotor into compartments or buckets, and serve to drive a ring of liquid, in the illustrative case liquid fuel, around in the casing. Since the liquid is thus subjected to centrifugal force, it recedes from the center of rotation as the lobe depth increases and is forced back toward the center by the outer lobe 'wall as the lobe depth diminishes. The outer boundary of the ring always coincides with the inner wall of the casing 14. The inner boundary of the ring is indicated by the dot and dash line 14c of FIG. 4a. A pocket is alternately expanded and contracted at the inner end of each bucket or compartment of the rotor during the traverse by the bucket of each of the lobes, vapor being caused to be drawn into the bucket through an intake port '36 formed in a stationary central cone 37 as the liquid moves outward, and being compressed and driven from the bucket through an outlet port 38 of the cone 37 as the liquid moves inward. Since the traverse of a single lobe completes the pumping cycle for each bucket, two diametrically opposed inlet ports 36 and two diametrically opposed outlet ports 38 are provided in the cone 37, so that each lobe has an inlet port and an outlet port associated with it.

The cone 37 forms an integral part of a stationary head section 39 which has passages 40 therein that communicate with the ports 36, and passages 41 therein that communicate with the ports 38. The left hand face of the head section 39 is generally open and is covered by a ported disc 42. The casing member 2 carries the body member 14, the head member 39, and the ported disc 42.

Body member 14 is composed of the annular ring 13, lobes 33 and 34, head section 39 and ported disc 42, which are all formed into one integral part by furnace brazing. Studs 43 are passed through the casing member 2, and have reduced ends threaded into the ring portion 13 of the body member 14. Nuts 45 are threaded onto the studs 43 for holding the body members 2 and 14 together. Dowel pins 46 are passed through the disc '42 and the head member 39 and into the annular ring 13 for maintaining the alignment and orientation of these parts during the brazing process.

The casing member 2 is provided with vapor inlet passages 47 and with vapor outlet passages 43 which communicate respectively with the inlet passages 46 and the outlet passages 41 of the head member 39. The passages 47 and 48 also communicate with inlet and discharge passages 49 and 50, respectively, which are formed in the casing member 3.

The liquid fuel, with its entrained vapor, enters the eye of the impeller at 5.1. As explained in Serial No. 652,633, the liquid pump is especially designed to cause the gas and vapor to be separated from the liquid and to be collected in an annular channel 52 which is formed in the liquid pumping chamber of the casing member 3. The vapor and gas are sucked out from the channel 52 through bores 52x and 53, a channel section 54 formed in the casing member 3, a channel section 55 formed jointly in the casing member 3 and a cover plate 56, and thencethrough the passages 49, 47 and 44 to the pumping chamber of the compressor.

The liquid fuel is freed of entrained gas and vapor by the combined action of the liquid pump and the compressor, and is then discharged through a volute passage 57 to a discharge conduit 58. In passing from the passage 57 to the conduit 58, the liquid automatically has its pressure reduced by reducing valve mechanism 59 to substantially a predetermined gauge pressure regardless of the speed at which the engine is operating.

The valve mechanism is mounted in the conduit 58, being carried by a supporting plate 60. The plate 60 is detachably secured along with a cover plate 61 to the portion of casing 3 which forms an end of the conduit 58 by machine screws 62.

The plate 60 is connected in sealed relation to one end of a corrugated bellows wall 63. The opposite end of the bellows wall is connected to a movable valve body 64 which is composed of complementary members 65 and 66. The bellows is closed at its forward end by the piston, but the bellows is open at its rear end and communicates with the atmosphere through passages 67, 68, 69,- 70, 71, 72 and a vertical drain tapping 72x at the bottom of casing member 2.

The valve body 64 slides in a cylindrical member 73 which is fixed in the conduit 58. The liquid fuel discharged from the volute passage 57 enters a circumferential channel 74 of the valve formed externally of the valve body, through an opening 75 which is provided in the cylindrical member 73. The channel 74 normally extends to the left of the cylindrical member 73 and communicates through openings 76 with the conduit 58. A stop shoulder 77 stands in the Way of the valve body 64 to limit inward movement of the valve and prevent overextension of the bellows 63. The end of the adjusting screw stands in the way of the valve to limit outward movement of the valve and thereby prevent over-compression of the bellows.

A compression coil spring 78 bears at one end against the valve body 64 and at the opposite end against a flanged and shouldered nut 79. The nut is threaded on the screw 80 which is mounted on the plate 61 with capacity for rotation, but not for axial movement. The screw is formed with a flange 81 which engages the inner face of the plate 61. A neck and head portion 82 of the screw extends through the plate 61, the protruding portion of the head being slotted. A boss 83 on the face 7 of plate 61 is slotted to provide a means of locking screw 80 with lockwire 84.

The flange of nut 79 has a fiat face which bears against a flat sided finger 85 that extends inward from the plate 61. The finger 85 prevents rotation of the nut 79. As the screw 80 is turned by the head 82, therefore, the nut 79 is prevented from turning, and hence is caused to be fed axially along the screw in one direction or the other according to the direction in which the screw is turned.

Liquid will flow from the volute passage 57 through the valve channel 74 and into the conduit 58 so long as the valve body is not moved far enough to the right to close the openings 76 completely. During operation, pressure of the liquid in the conduit 58 tends to move the valve body or piston 64 toward the right, and this is opposed by atmospheric pressure acting within the bellows and the pressure of the spring 78 hearing leftward against the piston. The absolute pressure in the conduit 58, therefore, will generally be substantially atmospheric pressure plus a predetermined amount which depends in value upon the adjustment of the nut 79. When the nut 79 is adjusted toward the left, the resistance of the spring 78 which will have to be overcome prior to cut off, is increased, and when the nut 79 is adjusted toward the right, the resistance of the spring 78, which will have to be overcome prior to cut off, is reduced. The former adjustment increases the gauge pressure within the conduit while the latter adjustment reduces the gauge pressure within the conduit.

There is a passageway 79a leading from the chamber beyond the discharge valve, back to the pump suction. The purpose of this passageway is to bleed ofi some of the fuel beyond the discharge valve chamber back to the pump suction for the purpose of better regulation of the discharge pressure. By continuously bleeding off a slight amount of the fuel, the pressure is prevented from reaching undesirable limits when the control valve itself is closed and has done all of the regulating it can.

There is some liquid which is discharged by the vapor pump beyond the control valve and at times of operation where the control valve is closed, the discharge pressure developed by the vapor pump may be too high for the engine fuel system. By bleeding off this small amount of liquid, the ultimate discharge pressure is prevented from going to too high a limit.

Because of the pressure reduction effected by the valve 59, the compressor itself can operate at a lower discharge pressure than would otherwise be necessary if it were required to discharge against the full centrifugal pump pressure. The purpose of this valve is primarily for regulation of the fuel pressure and advantage is taken, as long as the valve is required in the circuit, to discharge the vapors to the reduced pressure.

The aircraft designer may cause the compressed gas and vapor to be discharged into the conduit 58 which leads forward to the inlet of the main engine pump, or to be returned to a fuel tank, whichever is more convenient.

If the compressor output is to be returned to a fuel tank, the cover plate 56, as shown in FIGURES 4 and 6, is applied to the casing member 3. The upper and lower halves of the plate 56 are divided from one another by a horizontal partition 87 which divides a lower pocket 88 from upper pockets 89 and 90. The partition 87 coincides with a partition Wall 91 of the casing member 3. The upper pockets 89 and 90 are divided from one another by a vertical imperforate partition 92 which coincides with a partition wall 93 of the casing member 3. The lower pocket 88 forms a part of the conduit section 55 through which communication is established between the groove 52 of the centrifugal liquid pump and the intake side of the compressor, as already described.

When the plate 56 is used, passage of the vapor and liquid from the pocket 90 to the pocket 89 is prevented by the imperforate partition 92. The liquid, therefore,

cannot pass from the discharge passage 50 to the conduit 58 by way of the pocket 89. In this case, a closure plug 94 is unscrewed from the end of the passage 50, and a tube is secured in its place for connecting the passage 50 with a fuel tank.

When it is desired to send the compressed gas and vapor forward through the conduit 58, however, a cover plate 56a is used in place of the cover plate 56, and the plug 94 is secured in place, as shown in FIGURE 2. The plate 56a is like the plate 56, being provided with partitions 87a and 92a which divide the inner side of the plate into pockets 88a, 89a and 90a. The only difference between the two plates resides in the fact that the partition 92a has a bore formed in it for placing the pockets 89a and 90a in communication with one another. This places the pocket 89a in communication with the outlet passage 50 of the compressor. The pocket 89a always communicates directly with the conduit 58 and hence transmits the products from the compressor into the conduit 58. In this case the plug 94, rather than a tube is applied to the interiorly threaded end of the passage 50.

The plates 56 and 56a are not necessarily mutually distinct structures. The plate 56 may be converted to the plate 56a simply by making a bore 95 through the partition 92. The plate 56a may be converted back to the plate 56 by plugging the bore.

The pump of FIGURE 8 differs from the pump of FIG- URES 1 to 7 primarily in the fact that the discharge pressure of the compressor is caused to be at least as great as the unthrottled output pressure of the centrifugal pump, so that no throttling of the centrifugal pump output is required in order to permit the compressor output to be combined with the centrifugal pump output.

All the parts of the pump of FIGURE 8 are found in FIGURES 1 to 7, and in general the principle of operation is the same. Corresponding reference characters have accordingly been applied to corresponding parts with the subscript b added in each instance. No comprehensive, detailed description will be given, but attention will be confined to the points of difference with particular emphasis upon the salient novelty of the FIGURE 8 form of pump.

The pump of FIGURE 8 is characterized by the fact that the blades 9b of the compressor rotor are made approximately as large in diameter as or, as shown a little larger than the blades 8b of the centrifugal pump impeller. This is brought about by generally increasing the radial dimensions of the compressor part in proportion to the centrifugal pump part, and by adjusting the communicating passages slightly to maintain the operative relation of the centrifugal pump and the compressor previously described.

The desired output pressure relationship could be brought about by relatively increasing the speed of the compressor. For lightness, compactness and simplicity, however, the driving of the pump impeller and the compressor rotor in unison from a common shaft is found advantageous. In that kind of an organization the rotor diameter must be approximately the same as the impeller diameter if the compressor output pressure is to equal or exceed the centrifugal pump output pressure.

As before, the entrained gas and vapor are separated from the liquid fuel at the intake side of the liquid pump, are drawn off by the compressor, compressed, and discharged to the conduit 50b. The conduit 50b, as before, may be closed ofl? from communication with the conduit 58]; by a cover plate like the plate 56 of FIGURE 6, in which case the plug 94b would be removed from the internally threaded end of the conduit 50b and replaced by a tube which leads to a fuel tank.

Alternatively, however, the plug 94b may be used to close the internally threaded end of the conduit 50b, and conduit 59b may be caused to deliver to the conduit 58b through a cover plate like the cover plate 56a of FIG- URE 7. The significant feature of FIGURE 8 resides in the fact that the discharge pressure of the compressor is at least as great as that of the liquid pump. No throttling valve is required in the conduit 58b, therefore, for enabling the compressor output to be delivered to and intermingled with the liquid pump output, and none is provided.

For limiting the pressure supplied at the intake of the main fuel pump, a throttling valve may be provided at the intake of that pump, but this valve acts impartially upon the previously combined outputs of the compressor and the centrifugal pump, and not upon the output of the liquid pump to the exclusion of the compressor.

The compressor of FIGURE 8 consumes relatively more power than the compressor of FIGURES 1 to 7. The FIGURE 8 combination has a wider range of usefulness, however, than the combination of FIGURES l to 7 because it can be applied in a wider range of installations, wherein a recombination of liquid pump and compressor outputs is required.

In 'FIGURES 9 to 12, the invention is illustrated as embodied in a combined liquid pump and compressor unit in which the liquid pump is of the duplex type. Here the liquid pump is divided axially into two pumping chambers having separate inlets but a common outlet. The vapors separated in the respective intakes are separately draw off by the respective lobes of the compressor, the compressor having distinct intake connections to the two lobes but a common outlet from them. The lobes of the compressor are caused thus to exert their suction effects separately upon the vapor collection channels of the respective centrifugal pump chambers, causing each to be effectively and independently evacuated, as pointed out in Serial No. 652,633.

The liquid pump output is throttled as in the illustrative case of FIGURES 1 to and 7, and the compressor output is fed forward and combined with the throttled liquid pump output en route to the main engine pump.

The liquid pump of FIGURES 9 to 12 comprises a body composed chiefly of body members 101, 103 and 105. The body member 101 supports the other body parts, being formed with a supporting flange 109 provided with bolt holes 111 through which it may be attached to the engine body. The body member 101 is also provided with tapped bores 113 for receiving machine screws (not shown) through which connection may be made to a flanged fuel supply pipe (not shown).

The body member 101 is formed with a generally cylindrical opening in which portions of the body members 103 and 105 are received. The body member 103 includes a flanged end closure plate 115 through which it is attached to the body member 101 by screws 117. The body member 105 similarly includes a flanged end closure plate 119 through which it is secured to the body 1118.1 ber 101 by screws 118 whose shanks also pass through an attaching flange 121 of compressor head member 123 for securing the head 123 along with the plate 119 to the body member 101. A flanged, cup-like compressor body member 125 is secured to the head 123 by screws 127.

A shaft 131 is equipped with a splined driving portion 133 through which it may be connected to be driven by the engine itself. The shaft is supported near one end in a bearing 135 which is carried by the plate 115 and near the other end in a bearing 137 which is carried by the plate 119. The bearing 137 is confined against axial movement between a shoulder 139 of the plate 119 and a split resilient ring 141 carried by the plate 119. A collar 143 disposed on the shaft 131 with its left face in engagement with a split resilient ring 145 that interfits with the shaft, has its right face disposed to bear against the bearing 137.

To the right of the bearing 137 there are successively provided on the shaft a collar 147, a sleeve 149, the hub of compresor rotor 151, a washer 153, and a nut 155. The nut 155 and the washer 153-clamp the rotor hub firmly against a shoulder 159 of the shaft. The collar 147, the sleeve 149, and the hub of the rotor 151 fill the space from the shaft end to the bearing 137 snugly enough to prevent end play of the shaft, but not tightly enough to cause binding or objectionable frictional resistance to rotation of the shaft. A key 157 provides a driving connection between the shaft 131 and the rotor 151.

Between the bearings and 137 the shaft has fixed to it the centrifugal pump impeller 161. The impeller 161 comprises a central hub 163 which is connected to the shaft 131 through a key 165. The hub is confined on the shaft between collars 167 and 169. The collar 167 bears against a shouldered collar 171 which is integral with the shaft. The collar 169 bears against a resilient split ring 173 which is interlocked with the shaft. The spacing is such that the hub is held between the shouldered collar 171 and the split ring 173. The impeller is driven by key 165. The hub 163 has integral with it a central partition flange 175 upon which the impeller blades 177 and 178 are mounted.

Liquid fuel with entrained gas and vapor enters the centrifugal pump through an opening 179 formed in the body member 10 1. It divides as it enters the body, one portion going through passage 181 of the casing member 101 and passage 183 of casing member 103 to the eye of the impeller at the left hand side of the partition 175, and the other portion going through passage 185 of easing member 101 and passage 187 of casing member 105 to the eye of the impeller at the right hand side of the partition 175.

The two chambers of the centrifugal pump discharge the liquid in common to a volute passage 189 formed in the body member 101. The gases and vapors are separated from the liquid near the inner boundary of the impeller blades, being collected for the respective chambers 191 and 193 in annular channels 195 and 197. (See particularly FIGS. 9 and 11.) The channel 195 communicates through a passage 199 with a circumferential pas sage 201 which is formed jointly between the body members 101 and 103.

The channel 197 communicates through a passage 203 with a passage 205 which is formed jointly by the body members 101 and 105. The channel 201 is connected through passages formed in the body members 101 and 105 with the inlet passage 233 of the one lobe of the compressor and the channel 205 is connected through passages formed in the body members 101 and 105, through separate inlet passage 231 connecting to the other lobe of the compressor. The inlet passages 231 and 233 do not communicate with one another. In this way, the lower and upper lobes of the compressor are caused to act as separate suction means for drawing off the gas and vapor from the respective centrifugal pump chambers 191 and 193.

The compressed gases and vapors are discharged from the two lobes to a common outlet passage 235. The passage 235 is connected through passages to deliver the products of the compressor to a chamber 237 for recombination with the output of the centrifugal pump after the liquid from the centrifugal pump has had its pressure reduced by throttling.

The chamber 237, formed in the body member 101, includes a cylindrical extension 23 9 in which a throttling valve 241 is mounted. The throttling valve is designed .to reduce the pressure of the liquid passing from the volute 189 of the centrifugal pump to the chamber 237. The valve comprises a supporting plate 243 which, together with a cover plate 245, is clamped to the end of the cylindrical extension 239 by screws 24-7. The plate 243 is connected to a Sylphon bellows 249, the opposite end of the Sylphon bellows being connected to a body member 251 and .a valve body 253.

The body 253 also includes a complementary body member 255. The valve body is made slidable in a cylin- 11 der 257 which is secured in the chamber 237. The valve body members 251 and 255 jointly define an external circumferential passage or space 259.

An opening 251 formed in the cylinder 257 in line with the end of the volute 189 admits liquid to the space 259. Normally the liquid entering the space 259' flows out of this space at the forward end of the valve body through side passages 263. The liquid which thus enters the chamber 237 bears against the end of the valve body 253 and tends to force the valve upward toward a position in which communication between the space 259 and the chamber 237 would be cut off. The liquid in chamber 237 may pass through an opening 265 in the cylinder 257 to the space which surrounds the bellows 249.

The interior of the bellows 249 is vented to the atmosphere through a space 267 which is provided between the plates 24-3 and 245, a port 269 formed through the plate 243, and a passage 271 formed in a side extension of the body member 101. Atmospheric pressure, therefore, opposes the pressure of the liquid in the chamber 237, tending to hold the passages 263 open.

A compression coil spring 273 is provided for supplementing the resistance of the atmospheric pressure to closing of the passages 263. Means are provided for adjusting the pressure of the spring 273 against the body of valve 253. The spring 273 bears at one end against valve body member 255, and at its opposite end against a flanged nut 275 which is threaded on a screw 277. The screw 277 is secured with capacity for turning, but without capacity for longitudinal movement in the cover plate 245.

A screw flange 277a surrounds the screw shank and bears against plate 245. Above the flange the screw comprises a waist portion 280, a cylindrical head portion 281 and a polygonal head portion 283, the head portions being disposed to project through and beyond the cover plate 245. A raised boss 285 on the face of the plate 245 surrounds the head portion 281. A locking wire 287 is disposed in a slot (not shown) of the boss 285 and extends through the head portion 281 of the screw for normally retaining the screw in adjusted position.

The nut 275 has a fiat face that engages an inwardly extending fiat finger 289 of the cover plate 245. The finger 289 prevents rotation of the nut 275 so that the nut is caused to be adjusted in and out along the screw 277 according to the direction of turning of the screw. To increase the amount of pressure above atmospheric pressure which will be maintained in the chamber 237, the nut is adjusted downward, and to reduce that pressure, the nut is adjusted upward.

The pump body member 101 also includes a passage 291, which is in communication with the inlet of the main engine pump, which in turn also communicates with the discharge chamber of the pump by means of the check valve 293. This check valve serves as a by-pass means to allow fuel to pass through the pump casing from its inlet to its discharge with minimum pressure drop when the pump is for any reason rendered inoperative.

The valve 293 includes a stem 297 which is guided in a bore 299 formed in a plate 301. The plate 301 is secured to the body 101 by screws 303. The bore 299 is formed in an axially elongated central portion of the plate 301. The bore contains in its inner end a compression coil spring 305, which urges the valve 293 toward its seat with predetermined force. The valve normally closes the passage 307 through which the passage 291 and the volute 189 communicate, being urged closed by the predetermined force of the spring 305 and also being held closed by the pressure difference normally maintained by the pump while operating between the discharge pressure developed in the volute 189 and the suction pressure of its inlet and existing in chamber 307. Upon stoppage of the pump, due to any failure of its drive system or in the pump itself, the main engine pump can still pump fuel through the booster pump by overcoming the slight pressure difference caused by the spring 305, thus per- 12 mitting valve 293 to open and fuel to pass with a minimum pressure drop through the pump structure.

The pumped liquid, whether or not combinted with the compressor output is discharged from the chamber 237 to the main fuel pump through an opening 307 in the wall of the chamber.

I have described what I believe to be the best embodiments of my invention. I do not wish, however, to be confined to the embodiments shown, but what I desire to cover by Letters Patent is set forth in the appended claims.

I claim:

1. A fuel pressure booster pump for pumping fuel at or near its boiling point to an aircraft engine, comprising, a centrifugal liquid pump portion having an impeller adapted to be driven by the engine, said liquid pump portion including means for centrifugally separating vapor from the liquid fuel, said means including an annular vapor collection passageway surrounding and adjacent an inner portion of said impeller, a compressor portion of the centrifugal liquid ring type having a rotor, rotatable shaft means connected to drive the liquid pump impeller and compressor rotor in unison, the rotor of the compressor portion being of at least as great a diameter as the impeller to develop a discharge pressure at least equal to that of the liquid pump, said compressor portion opearting to draw off, compress and recondense vapor separated from the liquid fuel supply to the liquid pump and collected in said annular passageway about the inlet to said impeller, an outlet passage for said liquid pump, and means for conveying the recondensed vapor from the compressor portion directly to said liquid pump outlet passage and for recombining it with said liquid pump discharge at substantially equal discharge pressures.

2. A fuel pressure booster pump for engines according to claim 1 in which said compressor portion includes a rotor of greater diameter than said liquid pump impeller and said compressor portion is capable of delivering an output pressure at least equal to that of said liquid pump.

3. A fuel pressure booster pump for pumping fuel at or near its boiling point to an aircraft engine comprising a housing including a liquid pumping chamber portion having a central liquid inlet opening and an annular liquid discharge passage terminating in a liquid discharge opening, a rotatable main shaft centrally mounted in said housing in said liquid pumping chamber portion, a liquid impeller having radial vanes affixed to said shaft and arranged in said liquid pumping chamber portion to take liquid in through said inlet opening and discharge it through said liquid discharge passage and said discharge opening at increased pressure, said liquid pumping chamber portion including means to centrifugally separate entrained vapor from the liquid passing through said liquid inlet opening, said means including an annular vapor collection passageway surrounding and adjacent an inner portion of the vanes of said impeller, a liquid ring compressor chamber portion defined within the interior of said housing including a rotor afiixed to said shaft and arranged in said compressor chamber portion, said rotor having a diameter at least as great as said liquid impeller diameter, vapor and gas inlet means for said liquid ring compressor chamber portion including an internal passage in said housing connecting said compressor chamber portion with said annular vapor collection passageway to continuously remove gas and liquid having entrained vapor from said liquid pumping chamber portion, and a discharge passage directly connecting said compressor chamber portion and said liquid discharge passage whereby the vapor compressed and recondensed by said compressor chamber portion is combined with the liquid discharge.

4. A pump according to claim 3 including a by-pass passage defined in said housing connecting said liquid discharge passage and said compressor chamber portion 13 discharge passage, said compressor chamber portion discharge passage terminating in a separate discharge opening, and means to close off said by-pass passage.

5. A fuel pressure booster pump for pumping fuel at or near its boiling point to an aircraft engine comprising a housing including a liquid pumping portion having a central liquid inlet opening and an internal annular liquid discharge passage leading to a liquid discharge opening, a rotatable liquid impeller in said housing arranged to take in liquid through said inlet opening and discharge it through said liquid discharge passage and said discharge opening at increased pressure, means for oentrifugally separating entrained vapor from the liquid being pumped, said means including an annular vapor collection passageway surrounding said opening adjacent an inner portion of said impeller, a liquid ring compressor portion defined within the interior of said housing including a rotor in said housing, said rotor being approximately equal in diameter to said impeller to develop upon rotation a discharge pressure of condensed vapor at least equal to said liquid pumping portion discharge pressure, a vapor and gas inlet for said liquid ring compressor portion including an internal passage in said housing connecting said compressor portion inlet with said vapor collection passageway to continuously remove gas and liquid having entrained vapor from said passageway, a discharge passage for said condensed liquid and vapor directly connecting said compressor portion and said liquid pumping portion discharge, and means to rotate said impeller and said rotor.

6. A pump according to claim 5, wherein said rotor and said impeller are mounted on a common drive shaft.

7. A pump according to claim 5, including a separate compressor portion discharge opening, and wherein said discharge passage for condensed liquid and vapor connects said compressor portion discharge opening, a bypass passage defined in said housing connecting said liquid discharge pass-age and said compressor discharge passage, and means to close off said bypass passage.

References Cited in the file of this patent UNITED STATES PATENTS 2,500,227 Adams Mar. 14, 1950 2,553,066 Southern May 15, 1951 2,612,844 Grise Oct. 7, 1952 FOREIGN PATENTS 368.879 Italy Mar. 6, 1939 391,460 Great Britain Apr. 28, 1933 511,305 Great Britain Aug. 16, 1939 

